The invention resides in a gyrotron which comprises a cathode with an emitter ring, an acceleration anode, a resonator, an uncoupling conduit, a collector and also an arrangement for generating a solenoidal, static, axial, magnetic constant field.
Gyrotrons are high-powered microwave sources as they are needed for the heating of fission plasmas. Typically, their output power is about 1 MW and their frequency in the area of 100 GHz.
A basic gyrotron design is shown and described in Meinke-Gundlach "Taschenbuch der Hochfrequenztechnik" (publisher Springer, Berlin, Heidelberg, New York, Tokyo, 1986), pages 1982-1986. Particularly, high-power gyrotrons are considered suitable as supplemental heating devices for fission plasmas (see pages S17 and S18).
With magnetic fields, which are constant along the axes or which change in a highly monotonous or simply linear manner, the electric efficiency reached by gyrotrons is at this point 50%. At least for research application, an improvement of gyrotron efficiency is, therefore, not urgent at this time. However, the use of gyrotrons in the industry is of increasing interest so that their greater efficiency becomes economically important. Research in this direction has been performed by M. E. Read et al., and is described in IEEE Transactions Microwave Theory and Techniques, Vol. MTT-30, No. 1, January 1982 on pages 42 to 46 under the title "Experimental Examination of the Enhancement of Gyrotron Efficiencies by the Use of Profiled Magnetic Fields". The magnetic constant field in the resonator is increasing or decreasing in a highly monotonous manner, that is, it is linear. Such a field continuity is obtained by additional winding arrangements in the area of the resonator or by appropriately guiding the magnetic flux by means of iron structures.
In this manner, the efficiency of a gyrotron can be increased and this is achieved by transforming energy from the axial velocity component of the electrons, first into transverse energy of motion, which energy is subsequently extracted by the HF field. But, in this manner, a monoenergetically "consumed" beam is not generated.
It is the object of the present invention to provide a gyrotron with substantially increased overall efficiency that has an efficiency coefficient of close to 1 and to reduce the heat generated during the operation of the gyrotron to such a degree that little or no forced cooling is required during its operation.